Transparent conductive coatings are useful in a variety of electronics devices. These coatings provide a number of functions such as electromagnetic (EMI shielding) and electrostatic dissipation, and they serve as light transmitting conductive layers and electrodes in a wide variety of applications. Such applications include, but are not limited to, touch screen displays, wireless electronic boards, photovoltaic devices, conductive textiles and fibers, organic light emitting diodes (OLEDs), electroluminescent devices, and electrophoretic displays, such as e-paper.
Transparent conductive coatings such as those described in U.S. Pat. Nos. 7,566,360 and 7,601,406 and WO2006/135735 are formed from the self-assembly of conductive nanoparticles coated from an emulsion onto a substrate and dried. Following the coating step, the nanoparticles self-assemble into a network-like conductive pattern of randomly-shaped cells that are transparent to light.
In order to achieve low sheet resistances on the order of 100 ohm/sq or less, the coatings typically require sintering after pattern formation. Such sintering can be done by thermal treatment alone, but the temperatures required are generally too high for most flexible, polymeric substrates that are desirably used in commercial scale roll-to-roll processing. Sintering can also be done chemically by a separate processing step such as exposing the formed pattern to certain chemical washes or vapors. Examples include exposure to an acid or formaldehyde solution or vapor, as disclosed in U.S. Pat. Nos. 7,566,360 and 7,601,406, or to acetone or other organic solvents as disclosed in PCT/US2009/046243. Such separate chemical processing steps are costly, inconvenient and potentially hazardous to workers in a commercial scale production process.